    {-# LANGUAGE CPP #-}
    {-# LANGUAGE OverloadedStrings #-}

    --------------------------------------------------------------------------------
    --  See end of this file for licence information.
    --------------------------------------------------------------------------------
    -- |
    --  Module      :  Namespace
    --  Copyright   :  (c) 2003, Graham Klyne, 2009 Vasili I Galchin,
    --                 2011, 2012, 2014 Douglas Burke
    --  License     :  GPL V2
    --
    --  Maintainer  :  Douglas Burke
    --  Stability   :  experimental
    --  Portability :  CPP, OverloadedStrings
    --
    --  This module defines algebraic datatypes for namespaces and scoped names.
    --
    --  For these purposes, a namespace is a prefix and URI used to identify
    --  a namespace (cf. XML namespaces), and a scoped name is a name that
    --  is scoped by a specified namespace.
    --
    --------------------------------------------------------------------------------

    module Swish.Namespace
        ( Namespace
        , makeNamespace, makeNamespaceQName
          , getNamespacePrefix, getNamespaceURI, getNamespaceTuple
        -- , nullNamespace
        , ScopedName
        , getScopeNamespace, getScopeLocal
        , getScopePrefix, getScopeURI
        , getQName, getScopedNameURI
        , matchName
        , makeScopedName
        , makeQNameScopedName
        , makeURIScopedName
        , makeNSScopedName
        , nullScopedName
        , namespaceToBuilder
        )
        where

    import Swish.QName (QName, LName, newQName, getLName, emptyLName, getQNameURI, getNamespace, getLocalName)

    import Data.Maybe (fromMaybe)
    #if (!defined(__GLASGOW_HASKELL__)) || (__GLASGOW_HASKELL__ < 710)
    import Data.Monoid (Monoid(..))
    #endif
    import Data.Ord (comparing)
    import Data.String (IsString(..))

    import Network.URI (URI(..), parseURIReference, nullURI)

    import qualified Data.Text as T
    import qualified Data.Text.Lazy.Builder as B

    ------------------------------------------------------------
    --  Namespace, having a prefix and a URI
    ------------------------------------------------------------

    -- |A NameSpace value consists of an optional prefix and a corresponding URI.
    --

    data Namespace = Namespace (Maybe T.Text) URI

    -- data Namespace = Namespace (Maybe T.Text) !URI
    -- TODO: look at interning the URI

    -- | Returns the prefix stored in the name space.
    getNamespacePrefix :: Namespace -> Maybe T.Text
    getNamespacePrefix (Namespace p _) = p

    -- | Returns the URI stored in the name space.
    getNamespaceURI :: Namespace -> URI
    getNamespaceURI (Namespace _ u) = u

    -- | Convert the name space to a (prefix, URI) tuple.
    getNamespaceTuple :: Namespace -> (Maybe T.Text, URI)
    getNamespaceTuple (Namespace p u) = (p, u)

    -- | Equality is defined by the URI, not by the prefix
    -- (so the same URI with different prefixes will be
    -- considered to be equal).
    instance Eq Namespace where
      (Namespace _ u1) == (Namespace _ u2) = u1 == u2

    instance Ord Namespace where
        -- using show for the URI is wasteful
        (Namespace a1 b1) `compare` (Namespace a2 b2) =
            (a1, show b1) `compare` (a2, show b2)

    instance Show Namespace where
        show (Namespace (Just p) u) = show p ++ ":<" ++ show u ++ ">"
        show (Namespace _ u)        = "<" ++ show u ++ ">"

    -- | Create a name space from a URI and an optional prefix label.
    makeNamespace ::
        Maybe T.Text  -- ^ optional prefix.
        -> URI        -- ^ URI.
        -> Namespace
    makeNamespace = Namespace

    -- | Create a qualified name by combining the URI from
    -- the name space with a local component.
    makeNamespaceQName ::
        Namespace   -- ^ The name space URI is used in the qualified name
        -> LName    -- ^ local component of the qualified name (can be 'emptyLName')
        -> QName
    makeNamespaceQName (Namespace _ uri) = newQName uri

    {-
    nullNamespace :: Namespace
    nullNamespace = Namespace Nothing ""
    -}

    -- | Utility routine to create a \@prefix line (matching N3/Turtle)
    --   grammar for this namespace.
    --
    namespaceToBuilder :: Namespace -> B.Builder
    namespaceToBuilder (Namespace pre uri) =
      mconcat $ map B.fromText
      [ "@prefix ", fromMaybe "" pre, ": <", T.pack (show uri), "> .\n"]

    ------------------------------------------------------------
    --  ScopedName, made from a namespace and a local name
    ------------------------------------------------------------

    -- | A full ScopedName value has a QName prefix, namespace URI
    --  and a local part.  ScopedName values may omit the prefix
    --  (see 'Namespace') or the local part.
    --
    --  Some applications may handle null namespace URIs as meaning
    --  the local part is relative to some base URI.
    --
    data ScopedName = ScopedName !QName Namespace LName

    -- | Returns the local part.
    getScopeLocal :: ScopedName -> LName
    getScopeLocal (ScopedName _ _ l) = l

    -- | Returns the namespace.
    getScopeNamespace :: ScopedName -> Namespace
    getScopeNamespace (ScopedName _ ns _) = ns

    -- | Returns the prefix of the namespace, if set.
    getScopePrefix :: ScopedName -> Maybe T.Text
    getScopePrefix = getNamespacePrefix . getScopeNamespace

    -- | Returns the URI of the namespace.
    getScopeURI :: ScopedName -> URI
    getScopeURI = getNamespaceURI . getScopeNamespace

    -- | This is not total since it will fail if the input string is not a valid 'URI'.
    instance IsString ScopedName where
      fromString s =
        maybe (error ("Unable to convert " ++ s ++ " into a ScopedName"))
              makeURIScopedName (parseURIReference s)

    -- | Scoped names are equal if their corresponding 'QName' values are equal.
    instance Eq ScopedName where
        sn1 == sn2 = getQName sn1 == getQName sn2

    -- | Scoped names are ordered by their 'QName' components.
    instance Ord ScopedName where
        compare = comparing getQName

    -- | If there is a namespace associated then the Show instance
    -- uses @prefix:local@, otherwise @<url>@.
    instance Show ScopedName where
        show (ScopedName qn n l) = case getNamespacePrefix n of
          Just pre -> T.unpack $ mconcat [pre, ":", getLName l]
          _        -> show qn -- "<" ++ show (getNamespaceURI n) ++ T.unpack l ++ ">"

    -- |Get the QName corresponding to a scoped name.
    getQName :: ScopedName -> QName
    getQName (ScopedName qn _ _) = qn

    -- |Get URI corresponding to a scoped name (using RDF conventions).
    getScopedNameURI :: ScopedName -> URI
    getScopedNameURI = getQNameURI . getQName

    -- |Test if supplied string matches the display form of a
    --  scoped name.
    matchName :: String -> ScopedName -> Bool
    matchName str nam = str == show nam

    -- |Construct a ScopedName.
    makeScopedName ::
        Maybe T.Text  -- ^ prefix for the namespace
        -> URI        -- ^ namespace
        -> LName      -- ^ local name
        -> ScopedName
    makeScopedName pre nsuri local =
        ScopedName (newQName nsuri local)
                   (Namespace pre nsuri)
                   local

    -- |Construct a ScopedName from a QName.
    makeQNameScopedName ::
        Maybe T.Text   -- ^ prefix
        -> QName
        -> ScopedName
    makeQNameScopedName pre qn = ScopedName qn (Namespace pre (getNamespace qn)) (getLocalName qn)

    -- could use qnameFromURI to find a local name if there is one.

    -- | Construct a ScopedName for a bare URI (the label is set to \"\").
    makeURIScopedName :: URI -> ScopedName
    makeURIScopedName uri = makeScopedName Nothing uri emptyLName

    -- | Construct a ScopedName.
    makeNSScopedName ::
        Namespace     -- ^ namespace
        -> LName      -- ^ local component
        -> ScopedName
    makeNSScopedName ns local =
        ScopedName (newQName (getNamespaceURI ns) local) ns local

    -- | This should never appear as a valid name
    nullScopedName :: ScopedName
    nullScopedName = makeURIScopedName nullURI

    --------------------------------------------------------------------------------
    --
    --  Copyright (c) 2003, Graham Klyne, 2009 Vasili I Galchin,
    --    2011, 2012 Douglas Burke
    --  All rights reserved.
    --
    --  This file is part of Swish.
    --
    --  Swish is free software; you can redistribute it and/or modify
    --  it under the terms of the GNU General Public License as published by
    --  the Free Software Foundation; either version 2 of the License, or
    --  (at your option) any later version.
    --
    --  Swish is distributed in the hope that it will be useful,
    --  but WITHOUT ANY WARRANTY; without even the implied warranty of
    --  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    --  GNU General Public License for more details.
    --
    --  You should have received a copy of the GNU General Public License
    --  along with Swish; if not, write to:
    --    The Free Software Foundation, Inc.,
    --    59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    --
    --------------------------------------------------------------------------------